Replaceable Accessory for a Small Electrical Appliance and Method of Monitoring the Usage of the Accessory

ABSTRACT

The invention is directed to an accessory for a small electrical appliance, such as a brush attachment for an electric toothbrush or a shaving component for an electric shaving apparatus, including a data memory and a transponder. The accessory furthermore includes an electronic circuitry which modifies a value stored in the data memory each time it receives a corresponding signal. Also described is a method of determining the end of the period of use of the accessory.

This invention relates to accessories, in need of replacement from timeto time, for small electrical appliances, such as brush attachments forelectric toothbrushes or shaving components for electric shavingapparatus, as well as to a method of determining the period of use orthe end of the period of use (wear limit) of the accessory.

WO 03/054771 A1 discloses an electric toothbrush comprising a handpieceand a replaceable brush attachment. The brush attachment accommodates amemory in which an information identifying the brush attachment isstored. Furthermore, the brush attachment houses a transponder thatdelivers the information stored in the memory upon receiving aninterrogation signal from an interrogation station. The handpiece housesa microcontroller which is capable of computing the cumulated period ofuse of the brush attachment identified and writing it into the memory ofthe brush attachment. The handpiece is also equipped with an indicatingdevice enabling the need for replacement of a brush attachment to besignaled.

DE 102 47 698 A1 discloses an electric toothbrush comprised of a gripelement and a replaceable bristle head. The grip element is providedwith a display on which the end of use of the bristle head can be shown.

It is an object of the present invention to provide an accessory for asmall electrical appliance which enables the period of use of theaccessory to be determined readily, and to provide a simple method ofdetermining the period of use of the accessory.

This object is accomplished with an accessory having a data memory, atransponder and an electronic circuitry which modifies a value stored inthe data memory each time it receives a corresponding signal from thesmall electrical appliance. The value stored in the data memory is, forexample, a counter reading which corresponds, for example, to thecumulated period of use of the accessory. Given a predetermined maximumperiod of use of the accessory, it is also possible to store theremaining period of use, the end of the period of use, or a relativeperiod of use which is related to the maximum period of use.

Such an accessory has the advantage that the period of use is stored inthe accessory itself, that is, there is no need for the small electricalappliance to allocate various accessories to their respective periods ofuse. This advantage is of particular importance in connection with anelectric toothbrush whose handpiece is used by several family membersattaching their personal brush attachments, or in cases where ahandpiece is operated with different types of brush attachment, forexample, a cleaning brush and a massaging brush.

A small electrical appliance cooperating with the accessory preferablyhas a transmitting and receiving device known per se, which enables aninterrogation signal to be sent and a signal returned by the transponderof the accessory to be received. In this way the data stored, forexample, in the data memory of the accessory can be modified, read outand/or indicated on an indicating device. Data transmission between thesmall electrical appliance and the accessory can take place byhigh-frequency signals, for example, which preferably are transmittedinductively. In cases where an accessory has no power supply of its own,the transponder and the electronic circuitry are operated with a supplyvoltage obtained from the high-frequency field generated by the smallelectrical appliance.

A particularly simple construction of an accessory of the inventionutilizes as signal for modifying the stored value simply the supplyvoltage developing in the transponder each time the accessory reachesthe transmission range of the small electrical appliance, meaning thatit is coupled thereto, or when the small electrical appliance withcoupled accessory is switched on. In this way a simple use counter isobtained which records the number of uses.

Another construction of an accessory of the invention utilizes formodification of the stored value signals which the small electricalappliance emits during operation at one-second intervals, for example.In this manner, a simple use counter is obtained which records therunning time of the accessory accurate to the second.

In a preferred embodiment of an accessory of the invention, theelectronic circuitry in the accessory increments the counter readingstored in the data memory by one step each time the small electricalappliance is switched on or on each receipt of a corresponding signaluntil a maximum value is reached. It is however also possible for thecounter reading to be decremented from a predetermined value. The end ofthe useful life of the accessory can then be detected when the counterreading reaches ZERO. The respective counter reading is transmitted fromthe transponder to the small electrical appliance. The counter readingis stored in the accessory at least twice, that is, in two memory cells.

On each modification of the value stored in the data memory, theelectronic circuitry has to read out the current value of the datamemory, modify the value and write it back into the data memory.Preferably, a non-volatile memory, for example, an EEPROM, is used asdata memory. Writing into a memory cell of an EEPROM takes severalmilliseconds and is conventionally preceded by setting all the bits inthe memory cell to ZERO. If the power supply, that is, for example, thehigh-frequency field from which the electronic circuitry draws itsenergy, breaks down precisely during this time, the write operation isnecessarily aborted. In consequence, the memory holds a meaninglessvalue or the memory contents are lost.

Possible reasons for a failure of the high-frequency field are above allthat the user turns the small electrical appliance off again or replacesthe accessory, hence removing it from the small electrical appliance, orthe primary or secondary cell of the small electrical appliance isdepleted or supplies a voltage insufficient for building up thehigh-frequency field. The likelihood of the high-frequency field failingprecisely during the short interval of time when data is written intothe data memory may be low. However when the accessory is usedfrequently as intended, the likelihood of losing the contents of thedata memory increases, developing into an annoyance.

The method of the invention for determining the period of use or the endof the period of use of the accessory is based on the following idea:

The counter reading of the use counter must be present in a non-volatiledata memory at any time. Only in this way is it ensured that it cannotbe lost. Therefore, the data memory includes at least two memory cells,each holding a counter reading. A suitable data memory is an EEPROM, forexample. In a still unused accessory, each of the two memory cellscontains a maxim value or ZERO, for example. In addition, each memorycell holds an identifier which enables the electronic circuitry todetect whether or not the value stored in the memory cell is correct ormeaningful. This identifier may be in the form of an additional bit, forexample, which is stored in the memory cell together with the respectivecounter reading in a manner known in the art. When a meaningful value isto be modified in the one memory cell, it will not be overwritten by themodified value until it is sure that the other memory cell also holds ameaningful value.

The method of the invention will be explained in the following withreference to an embodiment illustrated in the accompanying Figureshowing a flowchart.

After the transponder has emitted a corresponding signal, that is, atleast a supply voltage, to the electronic circuitry, the electroniccircuitry reads the counter reading out from the first and second memorycell and establishes, by means of the identifier, whether the firstmemory cell holds a meaningful value. If this is the case, the counterreading of the first memory cell is loaded into a buffer memory anddecremented by 1, for example. Then the decremented counter reading isstored first in the second memory cell and then in the first memorycell. If the first memory cell contains no meaningful value, the counterreading of the second memory cell is loaded into the buffer memory anddecremented by 1. Then the decremented counter reading is stored firstin the first memory cell and then in the second memory cell.Subsequently, the new counter reading is transmitted from thetransponder to the small electrical appliance. This process sequenceensures that at the end both memory cells contain a meaningful valueprovided that one of the two memory cells contained a meaningful valueat the beginning of the process. In the event of failure of the supplyvoltage of the accessory during the process, it is ensured that at leastone of the two memory cells holds a meaningful value.

The small electrical appliance can indicate the received new counterreading on an indicating device which indicates, for example, theremaining number of uses of the accessory until it is in need ofreplacement, or the indicating device is not activated until the counterreading ZERO is transmitted, which signals that the accessory is worndown and should be replaced.

1-10. (canceled)
 11. A method of monitoring usage of an accessory for asmall electrical appliance, the method comprising: providing anaccessory including a data memory and a transponder; coupling theaccessory to a small appliance; modifying a value stored in the datamemory each time the accessory receives a corresponding signal from thesmall electrical appliance, wherein the value is indicative of accessoryusage.
 12. The method according to claim 11, further comprising:storing, in the data memory, at least two values with a correspondingidentifiers and corresponding to the usage of the accessory;determining, by means of the identifier, whether one of the two storedvalues is meaningful; and in response to determining that one of the twostored values is meaningful, overwriting the meaningful stored valuewith a modified value when the accessory is used.
 13. The methodaccording to claim 11, further comprising transmitting the stored valuefrom the transponder to the small electrical appliance.
 14. The methodaccording to claim 11, wherein providing an accessory comprises one ofproviding a toothbrush accessory and providing a shaving apparatusaccessory, and wherein modifying the stored value is performed inresponse to usage of the accessory with the small appliance.
 15. Themethod according to claim 11, wherein the stored value is modified toindicate at least one of a number of uses, a cumulative time of usage,and a projected end of usable life.
 16. The method according to claim11, wherein the signal received from the small, appliance comprises ahigh frequency induction signal.
 17. The method according to claim 11,further comprising displaying an indicator that the accessory should bereplaced, in response to the stored value reaching a predeterminedvalue.
 18. An accessory for a small electrical appliance comprising: anelectronic circuit disposed within accessory; a data memory coupled tothe electronic circuit within the accessory; a transponder coupled tothe electronic circuit and positional within the accessory to receivesignals from a small appliance with the accessory coupled to the smallappliances; wherein the electronic circuit modifies a value stored inthe data memory each time the transponder receives a particular signalfrom the small electrical appliance to which the accessory is coupled.19. The accessory according to claim 18, wherein the electronic circuitmodifies the value stored in the data memory each time the appliance isswitched on with the accessory coupled to the appliance.
 20. Theaccessory according to claim 18, wherein the value stored in the datamemory is a counter that corresponds to accessory usage.
 21. Theaccessory according to claim 20, wherein the electronic circuitincrements or decrements the counter by one unit upon each receipt ofthe particular signal until the counter reaches one of a maximum orminimum value indicative of the need to replace the accessory.
 22. Theaccessory according to claim 18, wherein the electronic circuit storesthe modified value in the data memory.
 23. The accessory according toclaim 18, wherein the data memory is an EEPROM having at least twomemory calls in which the counter can be separately can be separatelystored.
 24. The accessory of claim 18, wherein the small accessory isone of a brush attachment for use with an electrical toothbrush and ashaving component for use with an electrical shaving apparatus.